Why is it necessary to add lemon juice or citric acid to some home canned foods? - 5

Tomatoes have a pH (acid) level that is just above the line dividing high-acid foods and low-acid foods. It is important for the safety and quality of tomato recipes that the proper acid level is maintained. Since many factors can decrease the natural acidity in tomatoes, the addition of bottled lemon juice or citric acid helps ensure the correct acidification. Other foods that have lemon juice use it because the lemon juice helps the fruit to not darken with time. Bernice is allergic to citric acid so we don't use any lemon juice, with no adverse effect.

Recipes that include an adequate amount of vinegar (5% acidity) do not require additional acidification, such as salsa, tomato chutney, relish and pickles.